1. Field of Use
This disclosure is generally directed to the delivery of a functional material or lubricant to the surface of imaging members, photoreceptors, photoconductors, and the like.
2. Background
In electrophotography or electrophotographic printing, the charge retentive surface, typically known as a photoreceptor, is electrostatically charged, and then exposed to a light pattern of an original image to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on the photoreceptor forms an electrostatic charge pattern, known as a latent image, conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder known as toner. Toner is held on the image areas by the electrostatic charge on the photoreceptor surface. Thus, a toner image is produced in conformity with a light image of the original being reproduced or printed. The toner image may then be transferred to a substrate or support member (e.g., paper) directly or through the use of an intermediate transfer member, and the image affixed thereto to form a permanent record of the image to be reproduced or printed. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. The process is useful for light lens copying from an original or printing electronically generated or stored originals such as with a raster output scanner (ROS), where a charged surface may be imagewise discharged in a variety of ways.
The described electrophotographic copying process is well known and is commonly used for light lens copying of an original document. Analogous processes also exist in other electrophotographic printing applications such as, for example, digital laser printing and reproduction where charge is deposited on a charge retentive surface in response to electronically generated or stored images.
To charge the surface of a photoreceptor (P/R), a contact type charging device has been used, such as disclosed in U.S. Pat. No. 4,387,980 and U.S. Pat. No. 7,580,655, which are incorporated herein by reference in their entirety. The contact type charging device, also termed “bias charge roll” (BCR), includes a conductive member which is supplied a voltage from a power source with a D.C. voltage superimposed with an A.C. voltage of no less than twice the level of the D.C. voltage. The charging device contacts the image bearing member (photoreceptor) surface, which is a member to be charged.
Electrophotographic photoreceptors can be provided in a number of forms. For example, the photoreceptors can be a homogeneous layer of a single material, such as vitreous selenium, or it can be a composite layer containing a photoconductive layer and another material. In addition, the photoreceptor can be layered. Multilayered photoreceptors or imaging members have at least two layers, and may include a substrate, a conductive layer, an optional undercoat layer (sometimes referred to as a “charge blocking layer” or “hole blocking layer”), an optional adhesive layer, a photogenerating layer (sometimes referred to as a “charge generation layer,” “charge generating layer,” or “charge generator layer”), a charge transport layer, and an optional overcoating layer in either a flexible belt form or a rigid drum configuration. In the multilayer configuration, the active layers of the photoreceptor are the charge generation layer (CGL) and the charge transport layer (CTL). Enhancement of charge transport across these layers provides better photoreceptor performance. Multilayered flexible photoreceptor members may include an anti-curl layer on the backside of the substrate, opposite to the side of the electrically active layers, to render the desired photoreceptor flatness.
In recent years, organic photoreceptors have been widely used for electrographic purposes. This is because organic photoreceptors are easy to prepare at low cost and have the advantages of mechanical flexibility, easy disposability and environmental sustainability. However, the microcorona generated during repetitive charging damages the organic photoconductor, resulting in a rapid wear of the imaging surface and shortening the life of the photoreceptor.
To further increase the service life of the photoreceptor, use of overcoat layers has also been implemented to protect photoreceptors and improve performance, such as wear resistance. However, these low wear overcoats are associated with poor image quality in a humid environment as the wear rates decrease to a certain level. In addition, high friction associated with low wear overcoats in A-zone also causes severe issues with BCR charging systems, such as motor failure due to high friction/torque and blade damage. As well, toner or additive particles remaining on the photoreceptor after transferring could not be effectively cleaned by the cleaning blade. As a result, use of a low wear overcoat with BCR charging systems is still a challenge, and there is a need to find ways to increase the life of the photoreceptor with excellent image quality and charging performance.
An applicator to continuously apply functional material (such as paraffin oil) to the surface of the photoreceptor was disclosed in patent applications, U.S. Ser. No. 13/279,981 and U.S. Ser. No. 13/326,414 incorporated in their entirety by reference herein. The applied thin layer of functional material addresses A-zone deletion, alleviates chattering of the cleaning blade, and reduces toner/additive contamination on the BCR. However, as a roll-type design, the applicator is difficult to control the contact force of the roller surface against the surface of the photoreceptor or the BCR along the entire length during rotation, which affects the rate of diffusion of oil from the delivery roller and results in an uneven distribution of oil, particularly at the two ends of the photoreceptor or BCR surface. As a result, after long term prints, toner density across a page becomes uneven, thus the edges of the images sometimes become darker than the middle due to an excess amount of delivered oil. This can further cause the delivery roller to become contaminated with toner and additives over time due to inefficient cleaning of the surface of the photoreceptor (P/R) by the cleaning blade. Toner particles are eventually transferred to and contaminate the surface of the BCR.
In U.S. Ser. No. 13/437,472, a blade applicator to apply an ultra thin layer of liquid phase functional materials on the surface of a P/R or a surface of a BCR is described. The blade applicator is in contact with the P/R surface or the BCR surface in a trailing configuration. However, the friction between the applicator and the surface of the P/R or the surface of the BCR can cause the contact edge on the blade to wear and cause non-uniform diffusion of the functional material on the surface of the P/R or the surface of the BCR. In addition, long term wear of the contact edge of the blade can result in contamination of toner or additives which can lever the blade edge away from surface of the P/R or the surface of the BCR, creating areas on the surface of the P/R or the surface of the BCR where no functional material is applied. This can cause damage of cleaning blade and image failure.